Systems and methods for electro-hydrodynamic wind energy conversion

ABSTRACT

An electro-hydrodynamic wind energy conversion system is presented. The system includes a wind passage allowing wind flow. Further, the system includes a reservoir having an opening in communication with the wind passage and configured to hold a liquid. The system also includes an agitator coupled to the reservoir and configured to convert the liquid into droplets. Additionally, the system includes a charging system disposed substantially opposite the reservoir opening and configured to deposit an electrostatic charge on the droplets and draw the droplets into the wind passage. Moreover, the system includes a charge collector disposed at a distal end of the wind passage and configured to collect the electrostatic charge from the droplets.

BACKGROUND

Embodiments of the present disclosure relate to wind energy conversiondevices, and more particularly to electro-hydrodynamic wind energyconversion devices.

Traditional wind energy conversion devices like wind turbines includemultiple mechanical rotating or moving parts such as rotor blades,shafts, generators, gearboxes, brakes, and the like. Wind impinging onthe blades causes the blades to rotate. This rotation is converted intoelectrical energy by a generator that is coupled to the blades. Althoughthese wind turbines have proved to be highly successful in onshore andoffshore windy regions, they require expensive parts and are oftenviewed as unaesthetic objects. Moreover, as the mechanical wind turbinesinclude noisy rotating and moving parts, they are unsuitable for certainareas.

Recently, as an alternative to the mechanical wind turbines, wind energyconversion devices that work on the principles of electro-hydrodynamics(EHD) have been developed. These devices do not generate electricitythrough the motion of any moving parts; instead, they generateelectricity by generating small electrically charged liquid dropletsand/or solid particles and introducing them into the wind path. The windcarries the charged droplets and/or particles towards a collection grid,where the electric charge of the droplets is deposited. In thesesystems, the wind speed determines the number of liquid droplets and/orsolid particles carried away from the injection point per unit time, andtherefore the amount of electrical energy generated by the device. TheseEHD wind energy conversion devices are capable of generating electricityakin to the mechanical wind turbines without the added noise or movingparts. Moreover, these devices are inexpensive, aesthetically morepleasing, and simple to construct.

Existing EHD wind energy conversion devices, however, may not be veryefficient. Current technologies use a nozzle or electrospray to converta liquid into charged droplets. In these technologies, water ispressurized and sprayed out of a point source to form droplets. However,as the nozzles are point sources, they may not be able to produce alarge number of droplets or droplets having small dimensions optimal forEHD power conversion. The number and size of droplets are importantfactors affecting the efficiency of these devices as these factorsdirectly affect the cumulative power generated by the device. Forexample, if the drops are too large, the drag force of low speed windsmay be insufficient to carry the droplets effectively, and if the numberof droplets is too low, it may lead to lower power generation.

BRIEF DESCRIPTION

In accordance with aspects of the present disclosure, anelectro-hydrodynamic wind energy conversion system is presented. Thesystem includes a wind passage allowing wind flow. The system alsoincludes a reservoir having an opening in communication with the windpassage and configured to hold a liquid. Further, the system includes anagitator coupled to the reservoir and configured to convert the liquidinto droplets. In addition, the system includes a charging systemdisposed substantially opposite the reservoir opening and configured todeposit an electrostatic charge on the droplets and draw the dropletsinto the wind passage. Moreover, the system includes a charge collectordisposed at a distal end of the wind passage and configured to collectthe electrostatic charge from the droplets may also be present.

In accordance with another aspect of the present disclosure, a methodfor converting wind energy into electricity is presented. The methodincludes storing a liquid in a reservoir having at least one opening incommunication with a wind passage, where the wind passage allows windflow from a proximal direction to a distal direction. Further, themethod includes agitating the liquid in the reservoir to form dropletson a liquid surface. The method also includes depositing anelectrostatic charge on the droplets. In addition, the method includesdrawing the electrostatically charged droplets towards the wind passage.Also, the method includes transporting the electrostatically chargeddroplets towards a charge collector disposed at the distal end of thewind passage. Moreover, the method includes collecting the electrostaticcharge present on the droplets at the charge collector.

In accordance with yet another aspect of the present disclosure, anelectro-hydrodynamic wind turbine system is presented. The systemincludes a wind passage allowing wind flow. Furthermore, the systemincludes a substantially tubular guiding structure in line with the windpassage having a proximal end and a distal end and configured to allowthe wind flow. The system further includes a reservoir having an openingin communication with the wind passage coupled to a sidewall of theguiding structure and configured to hold a liquid. Moreover, the systemincludes an agitator coupled to the reservoir and configured to convertthe liquid into droplets. The system also includes a charging systemcoupled to the guiding structure. Additionally, the system includes thecharging system is configured to deposit an electrostatic charge on thedroplets, and draw the droplets into the guiding structure. Also, thesystem includes a charge collector disposed at the distal end of theguiding structure and configured to collect the electrostatic chargefrom the droplets.

DRAWINGS

These and other features, aspects, and advantages of the presentdisclosure will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a block diagram of an exemplary EHD system for use in a windturbine, in accordance with aspects of the present disclosure;

FIG. 2 is a flowchart illustrating an exemplary method for convertingwind energy into electricity, in accordance with aspects of the presentdisclosure;

FIG. 3 is a diagrammatic representation of an exemplary EHD system, inaccordance with aspects of the present disclosure;

FIG. 4 is a diagrammatic representation of another exemplary EHD system,in accordance with aspects of the present disclosure;

FIG. 5 is a diagrammatic representation of yet another exemplary EHDsystem, in accordance with aspects of the present disclosure; and

FIG. 6 is a diagrammatic representation of yet another exemplary EHDsystem, in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

Embodiments of the present disclosure are related to a system and methodfor electro-hydrodynamically extracting electrical energy from wind. Thesystems described hereinafter generate a large number of micron-sizeddroplets, which increase the cumulative charge generated by the system,and in turn enhance the efficiency of the system.

Conventional solutions that utilize electrosprays or nozzles to generatecharged droplets fail to produce a large number of droplets. Inparticular, in a conventional electrospray system pressurized liquid isdispensed through a pointed end of a nozzle to produce droplets, therebyresulting in the generation of a limited number of droplets. To increasethe number of droplets generated, these systems can increase the size ofthe orifices. However, increasing the size of the orifices results in anincrease in the droplet size. It may be noted that in certain cases nodroplets may be formed because of the large orifice size. Alternatively,these systems may increase the number of nozzles. However, increase inthe number of nozzles increases design and manufacturing complexities,and induces high drag. Consequently, these conventional systems fail togenerate sufficient number of droplets, and therefore fail to generatesufficient cumulative charge. To increase their efficiency, thesesystems may attempt to place a larger charge on each droplet byintroducing a large electrostatic field. However, the amount of chargethat can be effectively placed on a droplet is governed by Rayleigh'slimit. Beyond a certain charge value, increasing the charge on thedroplets reduces the efficiency of the system. Therefore, the efficiencyof these conventional systems is limited by their design.

The shortcomings of the presently available technologies may becircumvented by an exemplary EHD system. In accordance with variousembodiments of the exemplary EHD system, droplets are generated from thesurface of a liquid through liquid agitation, thereby substantiallyincreasing the number of droplets generated at any given time. Forexample, embodiments of the EHD system generate droplets in a range fromabout 10 million droplets per second per cm² to about 1000 milliondroplets per second per cm². Moreover, the size of the droplets is afunction of the agitating frequency, and therefore may be configurable.With the large number of droplets generated, voltage levels may belowered, charge per droplet may be reduced, and the system may stillachieve a higher cumulative charge.

FIG. 1 illustrates an exemplary embodiment of an electro-hydrodynamic(EHD) system 100. In a presently contemplated configuration, the EHDsystem 100 may include a reservoir 104. The reservoir 104 may include anopening 106 that is in communication with a wind passage 102 in whichwind blows in a particular direction (in FIG. 1, the arrow indicates thedirection of wind flow). In some embodiments, the wind passage 102 mayinclude a guiding structure (not shown in FIG. 1) that guides wind froma proximal end to a distal end; while in other embodiments, the windpassage 102 may not include any guiding structure and may merely includespace above the reservoir opening 106 where wind may pass. For thepurpose of this disclosure, the term proximal direction is used to referto a direction from which wind blows and the term distal direction isused to refer to a direction into which the wind blows. In a similarfashion, the term proximal end is used to refer to an end of the windpassage 102 into which the wind blows, while the term distal end is usedto refer to an end of the wind passage 102 at which the wind exits thewind passage 102.

Further, the system 100 may also include an electrostatic chargingsystem 108 that is operatively coupled to the reservoir 104 or theguiding structure. Alternatively, the charging system 108 may not becoupled to the reservoir 104 or the guiding structure. Instead, it maybe a standalone device placed relatively opposite the reservoir opening106. Additionally, the system 100 may also include a charge collector110 disposed distal of the reservoir opening 106 and the charging system108 in the wind passage 102 such that a face of the charge collector 110is substantially in the wind path. The reservoir 104 may be filled witha liquid 122. Further, an agitator 112 may be coupled to the reservoir104 and configured to sufficiently agitate the liquid 122 such thatsmall droplets form on a surface of the liquid 122.

In one example, the wind passage 102 may be the space between thereservoir opening 106 and the charging system 108 through which windblows. In some embodiments, the guiding structure may be present in thispassage 102 to guide the wind along a fixed path. In other embodiments,no physical guiding structure may be present in the wind passage 102.Moreover, in some embodiments, the reservoir 104 and the charging system108 may be normal to the wind passage 102 (as illustrated in FIGS. 3-5);while in other embodiments, the reservoir 104 and the charging system108 may be in line with the wind passage 102 (as illustrated in FIG. 6).

Also, the reservoir 104 may have any shape or size. For example, thereservoir 104 may be cylindrical, cuboidal, or polygonal. Furthermore,the reservoir 104 may have a liquid intake opening (not shown in FIG. 1)in addition to the reservoir opening 106. The liquid intake opening maybe situated along the surface of the reservoir 104. For example, theliquid intake opening may be situated on one or more of the sidewalls ofthe reservoir 104. In other embodiments, the liquid intake opening maybe situated at the bottom of the reservoir 104. Depending on the levelof the liquid 122 in the reservoir 104, the liquid intake opening mayautomatically open, allowing the liquid 122 to enter the reservoir 104.Alternatively, an operator may monitor the liquid level, and inparticular, when the liquid level falls below a threshold value, theoperator may open the intake opening, allowing the liquid 122 to enterthe reservoir 104. In other embodiments, liquid may be continuouslyfilled in the reservoir 104 at particular rate. It will be understoodthat various means and mechanisms exist to fill a reservoir with liquidand monitor the liquid levels. Any of these known mechanisms may beemployed in this system 100 without departing from the scope of thepresent disclosure.

Moreover, the reservoir 104 may be formed using an electricallyinsulative material such that the reservoir 104 does not interfere withthe working of the EHD system 100. Example materials may include glass,plastic, or polymers. In some instances, the reservoir 104 may be coatedwith a lubricious or non-stick material such as Teflon™(polytetrafluoroethylene) to prevent the liquid 122 from adhering to thereservoir walls. It may be noted that the reservoir 104 may betemporarily or permanently coupled to the guiding structure in the windpassage 102. Temporary coupling allows operators to remove the reservoir104 for cleaning, maintenance and/or replacement. Example temporarycoupling means include screw fit arrangements, luer-locks, snap-fitarrangements, and so on. Permanent attachment ensures that a fit betweenthe reservoir 104 and the guiding structure is secure such that thereservoir 104 may not be inadvertently detached from the guidingstructure during operation. Means of permanently fitting the reservoir104 to the guiding structure may include welding, gluing, or molding.

The charging system 108 may be an electrostatic ring, a rod or a plate,in some embodiments. In other embodiments, the charging system 108 maybe plasma or an electron beam. Further, as previously noted, thecharging system 108 may be disposed at a location substantially oppositethe reservoir opening 106.

The charge collector 110 may be a charge collection grid or mesh coupledto an electrical circuit. Alternatively, the charge collector 110 maysimply be a connection to ground. Considerable flexibility is affordedin the size and shape of the charge collector 110. For example, thecharge collector 110 may be shaped as a rectangular grid placed normalto the longitudinal axis of the wind passage 102. Positioning the chargecollector 110 as described hereinabove enhances charge collection fromdroplets exiting the wind passage 102. In other examples, the chargecollector 110 may be shaped as a concave or convex mesh withoutdeparting from the scope of the present disclosure. In case the chargecollector 110 is a ground connection, the charge on the droplets issimply driven to ground and the charge in the liquid remaining in thereservoir 104 may be utilized to produce a working current.

In addition to the elements described hereinabove, various othersystems, modules, or devices may be coupled to or be part of the EHDsystem 100 contributing to its function. For example, a yaw sensor maybe coupled to the EHD system 100 to monitor wind direction and align thewind passage 102 and the charge collector 110 in line with the wind anddistal of the reservoir 104, respectively. Similarly, a power supply maybe coupled to the charging system 108, where the power supply may beconfigured to provide the charging system 108 the required electrostaticpotential to cause charge separation in the liquid 122. In addition tothese elements, the system 100 may also include electrical connectionsbetween the various elements to complete a charging circuit. Forexample, in case the charge collector 110 accumulates charge, the chargecollector 110 may be coupled to a load 118 to produce working current.Also, the charging system 108 may be coupled to one end of a powersupply 120 configured to supply an electrostatic potential to thecharging system 108. Moreover, the other end of the power supply 120 mayalso be coupled to the load 118 to complete the electrical circuitbetween the charging system 108, the power supply 120, the chargecollector 110, and the load 118. In case the charge collector 110 isconfigured to simply ground the droplet charge, the load 118 may becoupled between the reservoir 104 and ground (not shown) and the powersupply 120 may be coupled to the charging system 108 and between thereservoir 104 and the load 118. The EHD system 100 may further includehumidity sensors (not shown in FIG. 1) to monitor the operatingconditions, wind speed sensors to monitor wind speed, lighteningprotection bars, and the like.

It may be noted that although FIGS. 1, 3-6 depict use of a one reservoirand one reservoir opening, use of multiple reservoirs and/or reservoiropenings in the EHD system 100 is also envisaged. Depending on therequired power output, the number of reservoirs and reservoir openingsmay be varied.

FIG. 2 illustrates an exemplary method for converting wind energy intoelectricity using the exemplary EHD system 100 of FIG. 1. It may benoted that the method of FIG. 2 is described with reference to thecomponents of FIG. 1. The method begins at step 202 where a windpassage, such as the wind passage 102 is provided. Subsequently, at step204, a liquid such as the liquid 122 is stored in the reservoir 104,where the reservoir 104 has at least one reservoir opening 106 incommunication with the wind passage 102. A liquid agitator, such as theagitator 112 may be configured to agitate the liquid 122 at a determinedfrequency, as indicated by step 206. In one embodiment, the frequencymay be in the range from about 1 MHz to about 1000 MHz. Such anagitation vibrates the liquid 122 causing small droplets to form on theliquid surface.

Moreover, at step 208, the charging system 108 applies an electrostaticfield on the liquid surface causing charge separation. The chargeseparation causes the liquid droplets to accumulate a positive ornegative charge on their surface. Also, a charge that is opposite to thecharge on the droplets is accumulated in the liquid left behind in thereservoir 104. For example, if the charging system 108 is at a positivepotential, a negative charge accumulates along the surface of thedroplets and a positive charge accumulates in the liquid remaining inthe reservoir 104. This negative charge causes the droplets to drifttowards the charging system 108, which is at a positive potential, asdepicted by step 210. The drag force of the wind blowing in the windpassage 102, however, exceeds the force of the electrostatic fieldbetween the charging system 108 having a positive potential and thenegatively charged droplets, thereby curtailing the movement of thedroplets towards the charging system 108. Instead, the droplets arecarried towards a distal end of the wind passage 102. Additionally, atstep 212, the charge collector 110 may either collect the negativecharge of the droplets or drive the negative charge to ground. In casethe charge collector 110 accumulates the negative charge of thedroplets, a load may be connected to the charge collector 110 to producea working current.

The following sections describe some exemplary embodiments of the EHDsystem 100 of FIG. 1. It will be understood that other configurationsmay just as easily be considered without departing from the scope of thepresent disclosure.

Turning now to FIG. 3, an exemplary EHD system 300 is presented. In thisexample, the system 300 includes a wind passage 302 with a guidingstructure 303, and a reservoir 304 disposed substantially normal to theguiding structure 303. Also, the reservoir 304 includes an opening 306,which is coupled to the guiding structure 303 and may be substantiallyas large as the width of the reservoir 304, in one example. In addition,a charging system 308 such as an electrostatic plate may be disposedover the reservoir opening 306. In other cases, the charging system 308may be an electrostatic ring having a diameter substantially equal tothe diameter of the reservoir opening 306. Moreover, an agitator, inthis embodiment, may include one or more piezoelectric crystals 312.Furthermore, in one example, the one or more piezoelectric crystals 312may be disposed at the bottom of the reservoir 304 and in contact with aliquid 318 present in the reservoir 304. A power supply 316 may providecharging voltage or current to the charging system 308. Moreover, acharge collector 310 such as a collection grid may be placed at a distalend of the guiding structure 303. This grid 310 may further be coupledto the power supply 316 through a load 314 to complete the chargingcircuit. A ground connection 317 may be provided between the chargecollector 310 and the load 314.

The guiding structure 303 may be a substantially hollow cylindrical tubehaving a proximal end 321 and a distal end 322. For purposes of thisdisclosure, the proximal end refers to an end of the guiding structure303 from where wind enters the wind passage 302 and the distal endrefers to the end of the guiding structure 303 from where wind exits thewind passage 302. Moreover, the guiding structure 303 may be largeenough to allow large amounts of wind to pass through the EHD system300. In addition, the guiding structure 303 may have a substantiallycircular, elliptical, rectangular, polygonal, or randomly shapedcross-section without departing from the scope of the presentdisclosure. In other embodiments, to increase wind velocity, the guidingstructure 303 may have a conical or tapered shape. It will be understoodthat the shape and size of the guiding structure 303 may varyconsiderably from application to application and therefore embodimentsof the present disclosure do not limit the scope of the size and shapeof the guiding structure 303.

Further, the guiding structure 303 may be formed using a graded plasticor polymer material. Example materials include steel, carbon fiber, PVC,aluminum, Teflon™ (polytetrafluoroethylene), plastics, nylon, or glass(metals, organic and inorganic materials).

With continuing reference to FIG. 3, the reservoir 304 may be couplednormal to the longitudinal axis of the guiding structure 303. In otherembodiments, however, the placement of the reservoir 304 with respect tothe guiding structure 303 may vary. For instance, the reservoir 304 maybe disposed outside the guiding structure 303 and normal to alongitudinal axis of the guiding structure 303. In this case, thereservoir opening 306 may be coupled to a side wall of the guidingstructure 303. Alternatively, the longitudinal axis of the reservoir 304may be parallel and substantially coincident with the longitudinal axisof the guiding structure 303. In this case, the reservoir 304 may beplaced within the guiding structure 303 or at the proximal end 321 orthe distal end 322 of the guiding structure 303.

In the system 300, the wide reservoir opening 306 allows a large numberof droplets to exit the reservoir 304 and travel towards the chargingsystem 308. Moreover, the reservoir 304 may itself be wider than tallerin some embodiments. Greater width allows a greater amount of the liquid318 to be converted into droplets and subsequently be carried to thecollection grid 310. It may be noted that the terms charge collector andcollection grid may be used interchangeably.

The piezoelectric crystals 312, when subjected to an electrical field,vibrate at a frequency dependent on the electrical field and the innateproperties of the piezoelectric crystals 312. To generate thesevibrations, the piezoelectric crystal 312 may be coupled to one or moreof an electric generator, an oscilloscope, a transducer, and/or anamplifier. These components generate appropriate sinusoidal signals toinduce vibrations in the piezoelectric crystals 312. In otherembodiments, a power supply may be coupled to the piezoelectric crystals312 along with systems that are configured to convert the power intoappropriate sinusoidal signals. Since the vibrations of thepiezoelectric crystals 312 are dependent on the amplitude of theelectric field, the frequency of the vibrations can easily be alteredduring operation by varying the electric field connected to thepiezoelectric crystals 312.

Moreover, during operation, the piezoelectric crystals 312 are vibratedat a determined frequency and the charging system 308 may be energized.Vibrations from the piezoelectric crystals 312 carry into the liquid 318and vibrate the surface of the liquid 318. When the vibration energy atthe liquid surface exceeds the surface tension of the liquid 318,droplets 320 are formed at the liquid surface. Sizes of these droplets320 depend on the vibration frequency of the piezoelectric crystals 312.Therefore, by varying the electrical field applied to the piezoelectriccrystals 312, the vibrating frequency of the piezoelectric crystals 312may change, which in turn alters the size of the droplets 320. In someinstances, the frequency of the piezoelectric crystals 312 is in theMegahertz range and such a frequency may facilitate formation ofdroplets 320 with diameters in a range from about 1 sub-micron to about100 microns.

In the present example, the charging system 308 is coupled to theguiding structure 303 at a location that is substantially opposite thereservoir opening 306. Also, the charging system 308 is configured togenerate an electric field around the liquid 318 in the reservoir 304 tocause charge separation at the liquid surface. This charge separation inaddition to generating charged droplets, aids in reducing the surfacetension of the liquid 318 and thereby increasing the droplet productionrate. The charge of the droplets 320 is opposite that of the chargingsystem 308 and the liquid left over in the reservoir 304. Beingoppositely charged to the charging system 308, the droplets 320 movetowards the charging system 308. The wind passage 302 and guidingstructure 303, however, are normal to the path of the droplets 320. Windin the wind passage 302 drags the droplets 320 towards the collectiongrid 310, where the electrostatic charge of the droplets 320 iscollected. The system 300 may form droplets 320 in a range from about0.10 billion droplets per second to about 100 billion droplets persecond from approximately a 10 cm×10 cm cross-section of liquid surface.This droplet formation rate is expected to be substantially higher thanthe rate of any conventional systems because in the system 300, thedroplets 320 are formed using the entire liquid surface.

In another embodiment, instead of the piezoelectric crystals 312, theagitator may be a spinning nonconductive disc. FIG. 4 illustrates anembodiment of a system 400 where the agitator is a spinningnon-conductive disc 402. Here, the charging system 308 is coupled to theguiding structure 303 at a location that is substantially opposite thereservoir opening 306, the disc 402 is disposed at the reservoir opening306 and coupled to the guiding structure 303, and the charge collector310 is disposed at the distal end of the guiding structure 303. Theelectrical circuit remains similar to that described with respect toFIG. 3.

The liquid 318 from the reservoir 304 is provided to a surface of thedisc 402 that is in communication with the wind passage 302. In oneembodiment, the disc 402 may have a small central aperture 403 connectedto the reservoir opening 306. Further, a liquid delivery tube 405 may beconnected between the aperture 403 and the reservoir opening 306 toprovide the liquid 318 from the reservoir 304 to the disc surface. Itwill be understood that in other embodiments, the liquid 318 may betransported to the disc surface through other means, such as multipleapertures on the disc 402, or a pipe that transports the liquid 318 fromthe reservoir 304 to the disc surface. Further, the amount of liquidtransported to the disc surface is controlled such that at any giventime, a thin layer of the liquid 318 is present on the disc surface.

The disc 402 may be coupled to a power supply (not shown) and a motor(not shown) that rotate the disc 402 at a high speed. When the disc 402rotates at a particular frequency, the centrifugal force of the disc 402spins the liquid 318 off the edges of the disc 402 to form droplets 320.The number of droplets and their size may be a function of the rotationspeed, size of the disc 402, thickness of liquid layer, or liquid type.It will be understood that the number of droplets 320 may be a functionof any other parameter just as easily without departing from the scopeof the present disclosure. For example, the size of the droplets 320 maybe a function of the power of the charging system 308. Further, the disc402 may be disposed in a horizontal orientation, having upward ordownward curved edges. In addition, the disc 402 may have asemi-parabolic or any other shape that assists in droplet formation. Insome embodiments, a lubricious or non-stick coating may be applied onthe disc 402 to assist the liquid 318 in sliding off the edges of thedisc 402 and preventing any liquid from adhering to the disc surface.

The charging system 308 deposits a charge on the droplets 320 generatedby the rotating disc 402, and the charged droplets move towards thecharging system 308. When these droplets 320 reach the wind passage 302and the guiding structure 303 the droplets 320 are dragged by the windin the direction of the charge collector 310 where the charge on thedroplets 320 is accumulated.

FIG. 5 illustrates another exemplary embodiment 500 of an EHD system inaccordance with some aspects of the present disclosure. The system 500includes a wind passage 502, a guiding structure 503, a reservoir 504, areservoir opening 506 in communication with the guiding structure 503, acharging system 508, and a charge collector 510. In the present example,the reservoir opening 506 is substantially smaller than the width of thereservoir 504. For example, if the reservoir width is in a range fromabout 1 mm to about 10 mm, the width of the reservoir opening 506 inthis embodiment may be in a range from about 0.01 mm to about 1 mm. Inparticular, the reservoir opening 506 may be narrow and tapered like anozzle 512 or orifice. In other embodiments, more than one nozzle 512may be provided. Further, in certain other embodiments, multiplereservoirs 504 and nozzles 512 may be coupled along the guidingstructure 503 or the wind passage 502. For example, to increase thepower output produced by the EHD system 500, two or more reservoirs 504and nozzles 512 may be incorporated.

The nozzle 512 may be in communication with the guiding structure 503.In addition, the nozzle 512 may be coupled to a sidewall of the guidingstructure 503. Further, the charging system 508 may be operationallycoupled to the guiding structure 503 at a location that is substantiallyopposite the nozzle 512. Moreover, the reservoir 506 may include amechanism to pressurize a liquid 516 or force the liquid 516 into thenozzle 512. These pressurizing elements may include pumps, motors, orother such means without departing from the scope of the presentdisclosure.

In addition, one or more piezoelectric crystals 514 may be coupled to aneck of the nozzle 512 and within the reservoir 504. These piezoelectriccrystals 514 may be configured to agitate the pressurized liquid as theliquid 516 travels towards the nozzle 512. When the liquid 516 reachesthe nozzle opening, the liquid 516 forms a convex meniscus. Thevibrations induced by the piezoelectric crystals 514 vibrate thismeniscus before the meniscus forms a drop, thereby breaking up themeniscus into a plurality of smaller droplets 518. By breaking themeniscus into the plurality of smaller droplets 518, the system 500generates an increased number of droplets 518 and also reduces the sizeof the droplets 518.

In conventional electrosprays, the droplet size is governed by the sizeof the opening and the velocity of the liquid exiting the opening. Inthis system 500, however, the droplet size is also governed by thevibration frequency of the piezoelectric crystals 514. Consequently, thesize of the droplets 518 exiting the nozzle 512 may be controlled byadjusting the frequency of the piezoelectric crystals 514. In this way,the system 500 can generate an increased number of droplets as comparedto a conventional electrospray system.

Moreover, the charging system 508 deposits a charge on the droplets 518forcing the droplets 518 to move towards the charging system 508. Thewind passage 502 that is disposed between the charging system 508 andthe nozzle 512 draws the droplets 518 towards the charge collector 510disposed at a distal end of the wind passage 502.

Another exemplary embodiment 600 of the EHD system is illustrated inFIG. 6. The system 600 includes a wind passage 602, a reservoir 604, anozzle 606, a charging system 608, a charge collector 610, one or morepiezoelectric crystals 612, and a power supply 614. In a presentlycontemplated configuration, the nozzle 606 is coincident with the windpassage 602. Additionally, the charging system 608 may be disposed at alocation that is approximately/substantially opposite the nozzle 606 andat a distance from the nozzle 606. Further, the charging system 608 maybe in line with the wind passage 602.

It may be noted that in the illustrated embodiment, a guiding structureis not present in the wind passage 602. It will be understood, however,that in other configurations, the guiding structure may be present inthe wind passage 602. For example, the reservoir 604 may be presentwithin the guiding structure and at a distal end of the guidingstructure. Further, the guiding structure may be sufficiently larger indiameter than the reservoir 604 such that sufficient wind is allowed topass around the reservoir 604.

Moreover, in the example depicted in FIG. 6, the charging system 608 isan electrostatic ring having a diameter substantially equal to orgreater than the diameter of the nozzle 606. Further, it will be notedthat multiple reservoir 604 and nozzle 606 systems may be utilized inthis system 600. The multiple reservoir and nozzle systems may bearranged in parallel to each other. In that case, the charging system608 may have a diameter substantially equal to the combined diameter ofan arrangement of the multiple reservoir and nozzle systems. Referencenumeral 616 may generally be representative of a distal end of the windpassage 602.

The charge collector 610 may be placed at a location that is distal ofthe electrostatic ring. Further, the piezoelectric crystals 612 may becoupled to the nozzle 606 and the power supply 614 may be coupled to thecharging system 608 and the reservoir 604. In one embodiment, thepiezoelectric crystals 612 may also be present within the reservoir 604to agitate the liquid. For example, the piezoelectric crystals may bepresent in the form of one or more wires, needles, disc, or rods withinthe reservoir 604.

In FIG. 6, the reservoir 604 is illustrated with one nozzle 606 forillustrative purposes. However, it will be understood that the EHDsystem 600 may include any number of nozzles 606 in actualimplementation. Droplets 620 are generated in a manner that issubstantially similar to the droplet generation method of FIG. 5.Piezoelectric crystals 612 vibrate a liquid 618 in the nozzle 606 andbreak up a meniscus into a plurality of small droplets 620. The chargingsystem 608 deposits a charge on these droplets 620 and the droplets 620move towards the charging system 608. As the charge collector 610 isdisposed beyond the charging system 608, the droplets 620 move beyondthe charging system 608 due to the force of expulsion from the nozzle606 or the force of the wind and impinge on the charge collector 610,where the charge of the droplets 620 is accumulated. Alternatively, thecharge collector 610 may simply be a connection to ground that groundsthe charge on the droplets.

It will be understood that the wider opening reservoir of FIGS. 3 and 4may also be placed within the wind passage 602 of FIG. 6 and windconversion may be performed as described hereinabove.

In accordance with certain aspects of the present disclosure, the liquidmay be any fluid that has low surface tension and can be electricallycharged. For example, water, soap solution, salt solution, ethanol, andmethanol may be used. The wind energy conversion device as describedherein may also be utilized for offshore applications. In such cases,the liquid may be seawater. Seawater has a high content of sodiumchloride, which aids in ionization and lowers the surface tension of thewater. In dry or low humidity conditions, the water droplets whiletravelling downstream towards the charge collection grid or ground mayevaporate leaving behind a salt crystal as a charge carrier. Therefore,seawater, which may be easily pumped from the offshore location, may besuitable for offshore applications.

In other embodiments, the liquid may be water with added impurities suchas dust, pollen, oil, polymer balls and so on. Impurities reduce thesurface tension of water and aid in charging the water droplets.

The various embodiments of the exemplary EHD system and method forconverting wind into electrical energy using the EHD systems describedhereinabove are expected to dramatically increase the efficiency of thewind conversion process. These systems may generate large amounts ofdroplets per second per cm² (about 10 million droplets per second cm² toabout 1000 million droplets second per cm²) to increase the cumulativepower generated by the wind energy conversion device for the same windspeeds as compared to currently available solutions. Moreover, thesystems described hereinabove may generate droplets of very small size(about 0.1 micron to about 100 microns) allowing low speed winds toexert force on the droplets and carry them to the charge collector.Further, because the system may generate a large number of droplets,lower charge may be deposited per droplet as compared to conventionalsystems. The lower charge per droplet results in low particle mobility,thereby increasing EHD power conversion efficiency. Also, the charge perdroplet may be maintained much below Rayleigh limit.

Furthermore, the skilled artisan will recognize the interchangeabilityof various features from different embodiments. Similarly, the variousmethod steps and features described, as well as other known equivalentsfor each such methods and feature, can be mixed and matched by one ofordinary skill in this art to construct additional assemblies anddisclosures in accordance with principles of this disclosure.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

The invention claimed is:
 1. An electro-hydrodynamic wind energyconversion system, the system comprising: a wind passage allowing windflow; a reservoir having an opening in communication with the windpassage and configured to hold a liquid; an agitator coupled to thereservoir and configured to convert the liquid into droplets; a chargingsystem disposed substantially opposite to the reservoir opening andconfigured to: deposit an electrostatic charge on the droplets; draw thedroplets into the wind passage; and a charge collector disposed at adistal end of the wind passage and configured to collect theelectrostatic charge from the droplets.
 2. The system of claim 1,wherein the agitator comprises a vibrating piezoelectric crystal.
 3. Thesystem of claim 1, wherein the agitator comprises a rotating disc. 4.The system of claim 1, wherein the wind passage comprises a guidingstructure having a longitudinal axis aligned in a direction of windflow.
 5. The system of claim 4, wherein a longitudinal axis of thereservoir is normal to the longitudinal axis of the guiding structureand the reservoir opening is coupled to a side wall of the guidingstructure.
 6. The system of claim 4, wherein a longitudinal axis of thereservoir is coincident with the longitudinal axis of the guidingstructure and the reservoir opening is coplanar with the distal end ofthe guiding structure.
 7. The system of claim 6, wherein the chargecollector is disposed distal of the charging system.
 8. The system ofclaim 1, wherein the liquid comprises at least one of seawater, water,ethanol, methanol, soap solution, or combinations thereof.
 9. The systemof claim 1, wherein the reservoir opening is approximately as large asthe width of the reservoir.
 10. The system of claim 1, wherein thesystem is configured to generate droplets in a range from about 10million droplets per second per cm² to about 1000 million droplets persecond per cm².
 11. The system of claim 1, wherein the diameter of thedroplets is in a range from about 0.1 micron to about 100 microns. 12.The system of claim 1, wherein the reservoir opening comprises one ormore nozzles, and wherein the one or more nozzles have a diameter thatis smaller than the width of the reservoir.
 13. The system of claim 1,wherein the charge collector is configured to drive the electrostaticcharge of the droplets to ground.
 14. An electro-hydrodynamic windturbine system, the system comprising: a wind passage allowing windflow; a substantially tubular guiding structure in line with the windpassage having a proximal end and a distal end and configured to allowthe wind flow; a reservoir having an opening in communication with thewind passage, coupled to a sidewall of the guiding structure, andconfigured to hold a liquid; an agitator coupled to the reservoir andconfigured to convert the liquid into droplets; a charging systemcoupled to the guiding structure and configured to: deposit anelectrostatic charge on the droplets; and draw the droplets into theguiding structure; and a charge collector disposed at the distal end ofthe guiding structure and configured to collect the electrostatic chargefrom the droplets.
 15. The system of claim 14, wherein the agitatorcomprises one or more piezoelectric crystals.